1. Field of the Invention
The present invention relates to a ring-based multi-push voltage-controlled oscillator, and more particularly to utilizing a plurality of delay cells to form a ring-based structure for multiplying the frequency of the output signal of the oscillator.
2. The Prior Arts
The A voltage-controlled oscillator (VCO) is needed for the local oscillator in the integration of a phase-locking loop (PLL) or a microwave communication system. The VCO is usually used with a mixer to reduce a radio frequency signal to a low frequency signal for demodulation or modulate the low frequency signal with the radio frequency signal for transmission. In a wired communication system, the VCO provides an important reference frequency for the local oscillator in the timing circuit, such as sampling, multiplexer or demultiplexer.
The prior art oscillator usually includes the architecture of an LC tank, but the main problem of the architecture is that the circuit can not widely tune the output frequency. Moreover, of the oscillator is considerably bulky.
Although the architecture of multi-push VCO was proposed before, it still used the LC tank, and thus not only the design of the multi-push VCO is not easy to implement but also the frequency tuning range of the multi-push VCO is limited. For a ring-base VCO, The frequency tuning range is wider, but the controlling frequency is still constrained.